Benchmark: timing 1000 iterations of None, Slasho, qr...
      None: 70 wallclock secs (69.60 usr +  0.00 sys = 69.60 CPU) @ 14.37/s (n=1000)
    Slasho: 61 wallclock secs (61.24 usr +  0.00 sys = 61.24 CPU) @ 16.33/s (n=1000)
        qr: 66 wallclock secs (65.80 usr +  0.00 sys = 65.80 CPU) @ 15.20/s (n=1000)